1. Field of the Invention
The present invention relates to a swash plate compressor for use in a vehicular air conditioning system. More particularly, it relates to a swash plate compressor, in which wear of the sliding surfaces of a piston and a cylinder bore is surpressed, without increasing the weight of the compressor.
2. Description of Related Art
Swash plate compressors are known in the art. For example, Japanese Patent Publication JP-A-7-180658 describes the construction of a known swash plate compressor. This compressor includes a cylinder block having a plurality of cylinder bores radially formed therein and arranged with respect to the central axis thereof and having a plurality of pistons, each of which is slidably received in a cylinder bore. Further, it includes a front housing, which is securely fixed to a front end surface of the cylinder block to form a crank chamber therebetween and a drive shaft axially extending through the crank chamber, such that the ends thereof are rotatably supported by the front housing and cylinder block, respectively, through radial bearings. Moreover, it includes a conversion mechanism, which comprises shoes, a swash plate, the drive shaft, and the pistons. The conversion mechanism is provided on the drive shaft within the crank chamber for converting a rotating motion of the drive shaft into a reciprocating movement of the pistons. The compressor also includes a cylinder head, which is securely fixed to a rear end surface of the cylinder block to form a suction chamber and a discharge chamber therebetween and a valve plate assembly, which is provided between the cylinder block and the cylinder head.
In operation, the drive shaft is rotated by the engine of a vehicle through a known belt and pulley arrangement. The rotation of the drive shaft is transferred to the swash plate, so that, with respect to the rotation of the drive shaft, the inclined surface of the swash plate moves axially to the right and left. The rotation of the inclined surface of the swash plate translates into reciprocating motion of the pistons. As the pistons reciprocate, refrigerant gas, which is introduced into the suction chamber from a fluid inlet port, is drawn into each cylinder and compressed. The compressed refrigerant gas is discharged to the discharge chamber from each cylinder bore through a discharge port and therefrom into an external fluid circuit, for example, a cooling circuit, through the fluid outlet port.
In such known swash plate compressors, when a suction stroke of a piston changes to a discharge stroke of the piston, the swash plate absorbs a large piston-inertial-force. Consequently, a force is transferred to the pistons, which is caused by a reaction force to the piston-inertial-force and is received from the swash plate through shoes. This reaction force causes the pistons to be partially pressed against an opening edge of the cylinder bore, in a radially outward direction; in other words, the pistons become inclined due to the rotation of the swash plate. As a result, in extreme cases, the reciprocating movement of the pistons is prevented.
Accordingly, in such known swash plate compressors, a swollen or flattened bore portion is formed on the front end surface of the cylinder block, and a portion of the piston, which passes beyond the cylinder bore during the suction stroke, is supported by the swollen bore portion of the cylinder block.
As a result of the undesirable wear of the opening edges of the cylinder bores, the occurrence of the inclination of the pistons against the central axis of the cylinder bore may be reduced. Further, as shown in enlarged portion 30xe2x80x3 of FIG. 4, forming single-step chamferred portion 42 on the opening edge of cylinder bore 41 has been proposed in the known compressors, described above. According to this proposal, when such swash plate compressors are manufactured, the process of inserting the piston into the cylinder bore may be somewhat simplified.
Nevertheless, in such known swash plate compressors, because the swollen bore portion is formed on the front end surface of the cylinder block, extra material is unnecessarily used in the manufacture of the cylinder block. Therefore, the weight of the compressor is unnecessarily increased. Further, forming single-step chamferred portion 42 on the opening edge of cylinder bore 41 may be insufficient to reduce the occurrence of the inclination of the pistons against the central axis of the cylinder bore, when the pistons reciprocate.
An object of the present invention is to provide a swash plate compressor, which has a structure to effectively reduce the inclination of the pistons against the central axis of the cylinder bore.
In an embodiment of the present invention, a swash plate compressor comprises a cylinder block having therein a plurality of cylinder bores, a crank chamber, a suction chamber, and a discharge chamber. A drive shaft is rotatably supported in the cylinder block. Each of plurality of pistons is slidably disposed within one of the cylinder bores. A swash plate is disposed in the crank chamber and is tiltably secured to the drive shaft. A bearing couples the swash plate to each of the pistons, so that the pistons are driven in a reciprocating motion within the cylinder bores upon rotation of the swash plate. A plurality of stepped, chamferred portions are formed in succession on an opening edge of each of the cylinder bores.
In another embodiment, a swash plate compressor comprises a cylinder block having therein a plurality of cylinder bores, a crank chamber, a suction chamber, and a discharge chamber. A drive shaft is rotatably supported in the cylinder block. Each of pistons is slidably disposed within one of the cylinder bores. A swash plate is disposed in the crank chamber and is tiltably secured to the drive shaft. A bearing couples the swash plate to each of the pistons, so that the pistons are driven in a reciprocating motion within the cylinder bores upon rotation of the swash plate. A ring-shaped member is fitted into each of the cylinder bores. Each ring-shaped member has a plurality of stepped, chamferred portions formed in succession in an opening edge thereof.
Other objects, features, and advantages will be apparent to persons of ordinary skill in the art from the following description of the invention with reference to the accompanying drawings.